The present invention relates to electric storage batteries comprising means for sensing the presence of electrolyte at a given preferred level, and more particularly to electric storage batteries having those sensing means disposed through the battery cover.
It has for many years been known that it is possible to sense the electrolyte level within an electric storage battery by electric means by disposing a probe through one of the walls of the battery so that it might contact the electrolyte within the battery when that electrolyte is at a preferred fill level or within a range of preferred fill levels. Generally, these battery testers or battery probes have been disposed through battery caps which are either inserted in pre-existing fill holes or threaded into holes which are specifically defined in the battery cover for this purpose. U.S. Pat. Nos. 1,453,602, 1,607,031, 2,056,578, 2,076,384, 2,148,657, 2,836,808, 3,314,060 and 3,653,017 all disclose battery electrolyte indicators which are disposed through caps on the top of the storage battery in which the electrolyte level is to be indicated.
More recently, a battery probe has been developed which is not threaded, but instead is forced into a recessed well defined in the battery cover. This well, which is substantially cylindrical, has defined at the bottom thereof an offset opening which is adapted to be pierced by a portion of the probe adapted to sense the electrolyte level. The probe itself comprises a cylindrical lead plug which has crimped to it a tin coated copper pin. The lower portion of the copper pin and the upper portion of the lead plug are molded in a plastic cylinder which allows the lead plug to protrude therefrom for a distance of approximately 3/8 of an inch. The upper portion of the pin is surrounded by a tubular plastic portion which is integral with and slightly offset from the axis of the cylindrical plastic portion described above. This tubular portion completely surrounds the upper portion of the pin and has defined on the outer surfaces thereof a plurality of annular projections. The uppermost surface of the tubular portion terminates in a flange having a larger diameter than the annular projections described above. When this prior art probe is inserted into the well described above, the offset cylindrical lead slug containing portion of the probe pierces the hole defined in the bottom of the well while the annular projections along the tubular portion of the probe form a tight mechanical seal with the sides of the well. The annular flange at the top of the probe engages the upper surface of the battery cover around the well, and prevents the probe from being inserted too far into the well. As a result, this prior art device countersinks the probe within a well formed in the battery cover, making a tight mechanical seal between a plurality of annular projections on the probe, and the walls of the battery cover.
Although providing certain savings in materials and workmanship, use of a battery probe of the type described above has given rise to certain difficulties. In particular, the fixed attachment of a sensing wire to the pin makes the entire probe assembly prone to being loosened or dislodged from its tight engagement with the battery cover. Since the seal which is formed is essentially a tight press fit, the vibration to which a storage battery is normally subjected may tend to dislodge the battery probe from the well resulting in undesired acid leakage from the battery. Alternatively, in the event that the battery cell directly below the probe is not properly vented, acid electrolyte may be pumped or otherwise may seep from the cell, again by seeping around the edges of the battery probe.